rOXSERVATIOX OF SKELETAL CALril M ATOMS niUOrcir LIFE 



227 



Table 4. — Rktkxtiox of Materxal Cai^cium Atoms by 



THE OkKSPRIXGS 



Xo. of litU'i- 



Age in days 



iu j?m 



Per cent oi 



motliers' activity 



present in the 



offspring 



X'uniber of 

 maternal atoms 

 present 



II 



III 



IV 



V 



S.25 



t).59 



5.50 



6.0 



4.25 



KtO 

 80 

 67 

 72 

 52 



9.91 

 7.25 

 5.69 



8.55 

 6.98 

 6.67 

 6.27 



100 

 73 

 57 



100 



82 

 78 

 73 



DISCUSSION 



a) Conservation of the calcium atoms of the outgrown skeleton through 

 life 



The fact that a very appreciable part of the skeletal calcium is preser- 

 ved in the outgrown animal throughout its lifetime results from experi- 

 ments carried out by Singer, Armstrong and Premer^^^\ by (J arlson^^^' ^'^^ 

 and by Bauer^'^'^^ Similar results were obtained in investigations on 

 the renewal of the mineral constituents of the skeleton, performed by 

 the present author and his assoc. who used ^ap as an indicator^''^^ 



From specific activity data of the plasma and the skeleton of the 

 outgrown rat, the percentage of renewable skeletal sodium was calcu- 

 lated by Bauer^^^*^ to amount to 30—40 per cent of the sodium present 

 (disregarding the extracellular sodium); a similar figure — 45 per cent — 

 is reported by Edelman^^*^^ and by Baden and Moore^-'"'\ Since sodium 

 is mainly an extracellular element, the specific activity of plasma sodium 

 decreases only slowly with time, not so the specific activity of calcium. 

 The calculation of the percentage of renewable skeletal calcium from 



15* 



